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Uses of Pi |
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In the world of math, and in everyday life, pi is used to calculate many useful quantities. By using pi, you can calculate the circumference, C, of a circle if you know its radius, r:
C = 2pr
The diameter, d, of a circle is twice the radius:
d = 2 x r
As a result, the circumference can also be written as:
C = pd
You will also need pi to calculate the area, A, of a circle:
A = pr2
or
A = pd2/ 4
The volume, V, of a cylinder can be calculated using the area, A, of the base and its height, h:
V = A x h
V= pr2 x h
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For the above circle: |
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Radius, r = 5 inches
Diameter, d = 2 x r = 10 inches |
We can calculate the circumference, C, in either of the following two ways:
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C = 2pr
C = 2 x 3.14 x 5
C = 31.4 inches |
C = pd
C = 3.14 x 10
C = 31.4 inches |
Similarly, we can calculate the area, A, using either the radius or the diameter:
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A = pr2
A = 3.14 x r x r
A = 3.14 x 5 x 5
A = 78.5 square inches |
A = pd2/4
A = 3.14 x d x d /4
A = 3.14 x 10 x 10 / 4
A = 78.5 square inches |
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For the above cylinder: |
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Radius, r = 5 in.
Diameter, d = 2 x r = 10 in.
Height, h =15 in. |
The volume of the cylinder is:
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V = pr 2 x h
V= 3.14 x 5 x 5 x h
V= 1177.5 cubic inches |
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